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| Year : 1995 | Volume
: 1
| Issue : 1 | Page : 46-55 |
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A Deficit Of Parental Consanguinity In Some Autosomal Recessive Diseases
Sarah Bundey
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Correspondence Address:
Sarah Bundey
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The observation of a deficit of a consanguineous parents in diseases thought to be inherited as autosomal recessives is as intriguing as a deficit of affected sibs. There are several possible explanations. The most likely is that new dominant mutations account for a proportion of patients, and this probably applies to all three diseases here. This explanation would also explain the reduced segregation in sibs. The second explanation is the most interesting, namely that neighbouring alleles are lethal in the homozygous state. This would lead to the non-ascertainment of consanguineous families in whom these "back" alleles co-existed. However this hypothesis would not explain a deficiency of affected sibs. The last explanation involves the action of mutant alleles (heterozygous or homozygous) at a second unlinked locus, which are essential for manifestation, but which do not cause disease on their own. The requirement of two pairs of unlinked recessive alleles for manifestation would give rise to a segregation ratio of 0.0625 or more, the requirement of two unlinked dominant loci would produce a segregation ratio of 0.25 and both situations would be associated with an unexpectedly low parental consanguinity rate. |
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